Inflammation plays an important role in cardiovascular disease, and the CD11/CD18 integrins are attractive targets for the development of new therapeutic agents. Complete inhibition of CD18, the common beta chain of the leukocyte integrins, profoundly reduces emigration of neutrophils (PMN) at sites of inflammation and leads to a severe immunodeficiency syndrome (leukocyte adhesion deficiency type I, LAD I). Although the genetic disorder LAD I has provided great insight into the functional significance of the CD18 family, the relative contributions of each of the CD11 integrins in the phenotypic abnormalities seen in LAD I remain unclear. Selective inhibition of specific CD11 integrins could potentially have therapeutic benefit in specific inflammatory conditions without broad impairment of host defense. In an effort to evaluate the function of each CD11 integrin, mice will be generated for use in two general experimental paradigms: First, to assess the functional consequences of the loss of a single CD11 integrin, and second, to assess the functions retained when a single CD11 integrin is present. The specific aims are: 1. Develop mice with specific deficiencies in each of the CD11 integrins and important combined mutations by targeted homologous recombination in embryonic stem cells. Mice have already been developed that are deficient in CD11a, CD11b, and CD11c. In order to better define the role of CD11 integrins in PMN function, the investigator proposes to make the double knockouts of CD11a + CD11b, CD11b + CD11c, and CD11a + CD11c, in which only a single CD11 chain is present on murine PMN, which lack CD11d. 2. Characterize the phenotypic changes due to selective deficiencies of the CD11 integrins with respect to neutrophil function. A combination of in vitro and in vivo studies will provide novel information on the functions of individual CD11 integrins in migration, adhesion, degranulation, hydrogen peroxide production, and cellular signaling, including interactions with the Fc receptors. 3. Characterize the contribution of each CD11 integrin on the host response to common bacterial and fungal pathogens in vitro and in vivo.